Abstract
Based on advanced light and electron microscopy, we describe the male reproductive system and sperm development of Limodromus assimilis. The genital tract consists of pairs of uni-follicular testes, spermatic ducts with diverticula regions, seminal vesicles, accessory glands, an unpaired ejaculatory duct and an aedeagus containing an internal sac equipped with sclerotic scales. Based on their morphology, we draw conclusions about their functions. After spermatogenesis within the follicle, the spermatozoa become released from the sperm cysts. The single spermatozoa move into the diverticula of the vasa deferentia I. Here, they become attached to central rods (spermatostyles), forming secondary conjugates (spermiozeugmata). The coordinated flagella movement of the conjugates possibly improves sperm velocity. Using super-resolution microscopy, we identified highly condensed reticulate chromatin in the lancet-shaped spermatozoa heads and the mitochondrial derivates of the flagella, likely formed by genomic and mitochondrial DNA, respectively. The results show, for the first time, sperm bundle formation in a Platynini species mainly corresponding to that found in Pterostichini species.
Highlights
Insect reproductive systems show large morphological variability
Based on advanced light and electron microscopy, we describe the male reproductive system and sperm development of Limodromus assimilis
The results show, for the first time, sperm bundle formation in a Platynini species mainly corresponding to that found in Pterostichini species
Summary
Insect reproductive systems show large morphological variability Their spermatozoa may vary strongly in shape and size [1, 2]. Some species form conjugates of spermatozoa, first identified by Gilson [4]. These were described in orders such as Odonata [5], Hymenoptera [6], Orthoptera [7] and Coleoptera [8]. In the three other taxa the spermatozoa heads are embedded in a hyaline carrier structure called a spermatostyle, central rod, carrier rod or cap. These structures may vary significantly in size, shape and number of spermatozoa included, even between closely related species
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